Back to OP's point, Challenge Tiers were inherently lazy design, but with good rewards. And yes, CT 2 and 3 rewards are good if you really loot at them. Maybe not as good as CT 1 but still worthwhile if you can.
The problem was they just dialed everything up to 11, speed and health in particular. I can use SLKR two turn stun with 530 speed SLKR, and the jedi will get two stun turns, then two more attacks before my slkr gets another turn. Essentially, CT3 they all have like 2k speed and 300k health.
So beating CT3 relies on an insane TM engine to counter their speed (EP, troopers, CLS) or some sort of abusive mechanic like SLKR / KRU health stacking.
At this point, all but Secrets and Shadows challenge tiers can be beat by developed rosters, but a lot of the fights are super tedious.
I know people hate on GC but in GC at least you can move first if you are fast enough.
But, in the end, there are a lot of rewards for ABs that weren't there before so that is acceptable.
